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The Future of DNA Profiling

Despite what procedural dramas might lead you to believe, the DNA that police collect at crime scenes can’t tell you anything about the characteristics of the person who left it behind. If police have a database of suspects’ DNA, then they can match a sample they’ve swabbed up on-scene with the profiles in the database. But the sample alone can’t tell them whether its owner had brown eyes or a propensity for diabetes. In fact, the inability to tell physical traits from law enforcement DNA databases is crucial to their legality: The Supreme Courtruled in 2013 that police are allowed to take DNA samples from people they’ve arrested for serious crimes—and doing so is not considered an unreasonable search—in part because the DNA markers that police look at “do not reveal an arrestee’s genetic traits and are unlikely to reveal any private medical information.”

A new study, however, begins to undermine that argument. A team of geneticists from universities in the United States and Canada found a way to match forensic DNA profiles with health-related DNA profiles. In other words, somebody with access to both U.S. law enforcement’s DNA database and a genetic research database could, theoretically, run an analysis to find if there’s anybody who pops up in both. From there, the analyst could look up traits such as that person’s ancestry and risk for diseases such as cancer and dementia.

“What we’re saying here is there’s this connection between databases that has not been part of the conversation about where policy should consider privacy,” says Noah Rosenberg, a genetics researcher at Stanford University and the study’s lead author.

Some outside experts contend that such matching might be much more difficult than it sounds. There are questions about how well Rosenberg and his team’s methods will work in the real world. Plus, a quirk in human DNA means it’s possible Rosenberg’s methods won’t hold up over time. “I think it’s unlikely to ever be useful,” says Sara Katsanis, a genetics policy researcher at Duke University whose own research was cited by the Supreme Court to support its argument that law enforcement’s DNA database doesn’t reveal important personal information.